Wiring up a compressor with starter

[Matt018888]

I finally moved into my shop, and started to put this Curtis compressor back together. I bought it from a dentist a couple of years ago. The original motor burnt up. I found a replacement motor that was the same hp, rpm, and bolt pattern. The only difference is it's a single phase motor. Anyways I wired it up the best I could but have a pressure switch off my pressure switch lol. I'm not sure what it does or where to hook it up on the starter. I believe maybe it's to release head pressure for a easy start up. Any help would be much appreciated.

 

[Matt018888]

I should add that I have fired it up and everything works and cycles. I just have to make a line from the one piston head to this other switch.

 

[MacMcMacmac]

The solenoid gets plumbed into the Swagelok fitting on the right head to unload the compressor with the inlet valve unloaders. This can be used to create a constant run machine, or just used to blowdown the head at shutdown. That's a Cadillac setup if it's working. Someone spent a good dollar on that. I love the crankcase breather. It's usually just a caged marble in there acting as a PCV valve.

 

[Matt018888]

The solenoid gets plumbed into the Swagelok fitting on the right head to unload the compressor with the inlet valve unloaders. This can be used to create a constant run machine, or just used to blowdown the head at shutdown. That's a Cadillac setup if it's working. Someone spent a good dollar on that. I love the crankcase breather. It's usually just a caged marble in there acting as a PCV valve.

Yes I bought it from a dentist who claimed the motor fried after a lightning storm. I bought it for a $100 bucks with the intent on making a wood stove for my hunting blind. But after testing the pump and it tested good I decided it was worth fixing. I found a 3hp lesson off a grain silo and it had the same specs. I just don't understand where to hook up the two black leads coming off this valve. I'd like it to just bleed off the head

 

[MacMcMacmac]

If you just need 120V to operate the solenoid, you can take it off of the switched hot leg from the pressure switch, through the solenoid, then back through the second spare contact to neutral. When the pressure switch trips, it should open the solenoid, which will send air to the heads and open the inlet valves to blow it down.

If you would rather a simpler system, you would need to buy a different pressure switch with a blowdown valve on the side and plumb it into a check valve with a blow down port on the side. This will necessitate the fabrication of a new discharge line to the tank.

 

[Matt018888]

If you just need 120V to operate the solenoid, you can take it off of the switched hot leg from the pressure switch, through the solenoid, then back through the second spare contact to neutral. When the pressure switch trips, it should open the solenoid, which will send air to the heads and open the inlet valves to blow it down.

If you would rather a simpler system, you would need to buy a different pressure switch with a blowdown valve on the side and plumb it into a check valve with a blow down port on the side. This will necessitate the fabrication of a new discharge line to the tank.

Yeah the parts you listed are similar to the ones I installed on a smaller compressor I built. I would like to use the parts I have as they seem to be of good quality I'm just unfamiliar with these designs. So the selinode need 110v to operate? Does this selinode stay closed untile pwr is supplied?

 

[MacMcMacmac]

You will have to determine that. It should say on the solenoid label what voltage it needs, and whether it's a normally open, or normally closed valve. What I described to you would be the simplest setup, but who knows? It may have had a separate 24VDC control setup, or any other number of things.

 

[Matt018888]

Ok, I have looked it over but the labels pretty worn

 

[MacMcMacmac]

You need to look at the aluminum plate on the top of the solenoid under the red hat.

 

[RTM]

The number on the label, 104r, is an ASCO 24v AC solenoid

https://www.grainger.com/product/ASCO-Solenoid-Valve-Coil-24V-AC-44U344

So that says somewhere you have a voltage step down transformer, or someone put the wrong solenoid on it, and that doesn't work.

 

[Matt018888]

The number on the label, 104r, is an ASCO 24v AC solenoid

https://www.grainger.com/product/ASCO-Solenoid-Valve-Coil-24V-AC-44U344

So that says somewhere you have a voltage step down transformer, or someone put the wrong solenoid on it, and that doesn't work.

I didn't know if I popped that red cover off and flipped the plate over there was info on it. Looks to be 120v I only have two black leads coming off it. I assume if I complete the circuit the selinode will open? I charged the system and no air came out... So normally closed?
By the way I appreciate your help!

 

[MacMcMacmac]

Ok, so now we know what we're dealing with. First of all, DO NOT energise this solenoid while it is off of the main body of the valve. They can burn up quick if the are powered up with nothing to work against.

This is a bit confusing. Normally, I would expect the solenoid to be normally open, so that when it is de-energised it would send air to the head unloaders. Try energising it with a 120V test cable and see what happens (safety first btw...). If there is no rush or air, you might have a bad solenoid, or you might have to futz with the screws. This is an ASCO Red Hat style I am not familiar with. The "meter" screws have me a bit confused. Have air in the tank and test the solenoid. There is an answer here somewhere.

As RTM suggested, this may be a 24V solenoid with the wrong data plate on it, who knows? If its burnt up, it's probably best to go with the check valve/bleed valve setup.

You are welcome for any help I can offer.

 

[Matt018888]

I don't believe it is 24v only because I was the one who unhooked it when I showed up for pickup. I don't remember seeing a transformer. I did have enough sense at the time to snap a pic of the inside of the starter box. You can see two 14gauge black wires run down the right side. The picture isn't perfect but it looks like they are pigtailed off a yellow wire nut. I don't see any transformer. But in the morning for the name of science I'll through a hot 120v lead on there and see if she blows lol.

 

[TurnipTruck]

Pry the lid off of the green solenoid housing and pull the actual electric coil out (may have to unwire it). If it is new enough, it will be molded black plastic and will have its required voltage cast into the plastic. If it’s older or lesser duty, it may have a voltage stamping somewhere on the wire insulation or the armature metal. Don’t lose the star washer between the lid and the coil!

 

[RTM]

If both the black wires are under the same wire nut, that would be bad too.

Ideally it should be wired into the pressure switch, and to a hot wire, and a ground, not in that order.

 

[Matt018888]

Ok, so now we know what we're dealing with. First of all, DO NOT energise this solenoid while it is off of the main body of the valve. They can burn up quick if the are powered up with nothing to work against.

This is a bit confusing. Normally, I would expect the solenoid to be normally open, so that when it is de-energised it would send air to the head unloaders. Try energising it with a 120V test cable and see what happens (safety first btw...). If there is no rush or air, you might have a bad solenoid, or you might have to futz with the screws. This is an ASCO Red Hat style I am not familiar with. The "meter" screws have me a bit confused. Have air in the tank and test the solenoid. There is an answer here somewhere.

As RTM suggested, this may be a 24V solenoid with the wrong data plate on it, who knows? If its burnt up, it's probably best to go with the check valve/bleed valve setup.

You are welcome for any help I can offer.

 

[Matt018888]

I put 110v to it and it made a buzz sound! I filled the tank with air held my finger over the selinode air out put and felt it slightly bleed air not a lot and this maybe why I missed it the first time. Than applied 110v to the selinode and felt as if in sucked my finger in. So I believe you are correct it's always open. I'm going to plumb in the head and give it a shot

 

[MacMcMacmac]

If it has a slight leak when energised, you may need to fix that, otherwise the line to the heads may pressurise while its running and you will unload. Sometimes you can disassemble the brass valve and flip over a rubber or teflon seat to get a fresh side to work with. Just get it running for now and see if it's going to be an issue first.

The return wire from the solenoid has to be wired through to a neutral, not ground.

 

[Matt018888]

I don't have a neutral. Just two hots and a ground

 

[MacMcMacmac]

Ok. I'm not an electrician, and I won't give any advice as to 3 or 4 wire 220V sockets and wiring. I'm sure going to the ground wire will work.

It always seemed a bit iffy to use the ground as a current carrying leg, but it seems to have been common practice as one point for 120V devices.

 

[Matt018888]

I'll swing by metro air in the morning and pick there brain. I have to see if they will make me the line from the compressor head to the selinode because that line was lost in the move. And has proved hard to get proper fittings than I anticipated

 

[MacMcMacmac]

The more I look at that valve, the more I think the screws are just throttling the air flow to each port. Port 2 looks like it is being used as an exhaust port to relieve the unloader system at start up, while port 3 is to the source for the air from the tank to unload the heads through the port that has the empty ferrule fitting on it. So an electric 3 way valve. Fairly elaborate setup for such a simple machine.

 

[Matt018888]

I got everything working great. Service tech at metro air said... The selinode is for bleed off the head. The metering screws control the duration of bleed off. The asco valve is opsolete. And they are expensive! The fitting off the head was metric compression and that's why I had a hard time finding anything. He only had one in stock. He did say running power to the asco selinode off the coil on the starter was good and earth ground would acceptable.

 

[MacMcMacmac]

Good to go!

 

[Matt018888]

Good to go!

Thanks for your help, I appreciate it!

 

[MacMcMacmac]

Glad i could help.